Skip to 0 minutes and 17 seconds SPEAKER 1: So, the importance of the immune system in fighting infection has been known for several hundreds of years. But can it also recognise and eliminate our own cancerous cells? In 1909, a physician and scientist called Paul Ehrlich predicted that one of the immune system’s jobs must be to prevent tumours. Otherwise, they would occur much more often than they do. For a long time, people were sceptical that the immune system could recognise cancer. But let’s look at six lines of evidence suggesting that, actually, it can. If our immune system does play an important role in fighting cancer, then it must follow that, if you have a poorly-functioning immune system, you are more likely to get cancer.
Skip to 1 minute and 4 seconds And we know that this is the case in several different scenarios. AIDS patients have a much weakened immune system due to the HIV virus, and they are much more likely to get certain types of cancer. Also, David Vetter, the “boy in the bubble” you may remember from last week, actually died of Burkitt’s lymphoma, a type of blood cancer. During stem cell transplantation for blood cancer, patients’ diseased blood cells are replaced by giving them blood stem cells from a closely matched, healthy donor. When this treatment works and cures the patient, it is actually the ability of T cells in the stem cell transplant to recognise and eliminate any remaining cancer cells that is crucial.
Skip to 1 minute and 53 seconds This strong immune response against a tumour even has a name– the graft versus leukaemia effect. In rare cases, it has been reported that infection can lead to regression of cancer. Early clinicians attempted to treat tumours by injecting a combination of bacteria into them, and it was thought that the body’s increased response to the bacteria also helped to fight the cancer. And today, injection of the BCG vaccine, which is usually used to vaccinate people against tuberculosis, into the bladder is used as a treatment for bladder cancer. It’s still not entirely clear how this treatment works, but it seems to encourage the immune activation in the lining of the bladder, which helps to kill off the cancer cells.
Skip to 2 minutes and 47 seconds As we also learned in week 1, immune cells are able to migrate out of the blood and crawl through the tissues of the body ready to fight disease. And, in some cancers, it’s been observed that, the more immune cells there are in the tumour, the slower the patient’s cancer progresses. In fact, in some cases, the immune signature inside the tumour might be an even better indicator of how the disease will progress than traditional methods used for staging cancer. On top of this, there is a lot of evidence showing immune cell recognition of cancer cells in the laboratory, and this gives scientists much hope for the future of immunotherapy development.
Skip to 3 minutes and 34 seconds And the final piece of evidence is arguably the strongest of all. It comes from some of the new immunotherapies that are already starting to transform cancer treatment. But you’ll hear more about this in week 3.
Evidence that the immune system can target cancer
In this video, Dr Heather Long discusses the immune system and whether, as well as protecting us from infection, the immune system can also kill cancer cells.
© Cancer Immunology and Immunotherapy Centre, University of Birmingham